Great improvements have been made in treating heart conditions, largely due to the research and development of new medicines. This post describes some of the most common ‘blood thinning’ medications often prescribed for people with a heart condition, including Warfarin. You may be prescribed some of these medications if you have had a heart condition such as valve surgery, arrhythmia, angina, heart attack, heart failure, heart rhythm disorders and heart valve disease. This page explains why you may have been given each medicine and how it works. It also describes the most common side effects.

This information is in conjunction to the advice that your doctors, pharmacists or nurses may give you based on their knowledge of your condition but it should help you to understand what they tell you. If you have any questions or concerns, always talk to your doctor or pharmacist. Never stop taking medication without talking to your doctor.

Anticoagulants

Blood clots are made up of platelets (tiny blood cells clumped together) and a protein called fibrin. If a clot is not treated, it could travel to the brain and cause a stroke, or travel to the lung and block a main artery (pulmonary embolism). Anticoagulants prevent fibrin from forming and so prevent harmful blood clots from forming. They are most commonly prescribed for people who have an abnormal heart rhythm, such as atrial fibrillation, or for those who have an artificial heart valve, as both these conditions increase the risk of having a stroke. Anticoagulants are also essential for treating clots that have already formed, such as those that develop in the veins of the legs (deep-vein thrombosis).

Heparin

Heparin is injected into a vein and has an immediate effect in preventing further blood clots from forming. This is known as intravenous heparin, and is usually given in hospital.

Another form of heparin called ‘low molecular weight heparin’ may be given subcutaneously (by injection just under the skin) over a longer period of time. This can be continued once the person returns home if it is needed. Some people can do the injection themselves, and sometimes a nurse or other health professional will do it.

Warfarin

What is Warfarin?

Warfarin is an anticoagulant that is given when long-term prevention of blood clotting is needed. Warfarin makes the blood thinner so that it doesn’t clot so easily. It is mostly used to prevent strokes in people with a heart condition or previous history of stroke.

Who takes Warfarin?

This medicine is most often used for people who have had a mechanical valve replacement, which currently means taking Warfarin for life. Some people also take Warfarin for an irregular heart rhythm, such as atrial fibrillation (AF), although there are newer drugs to replace Warfarin called Novel Anticoagulants so it is worth asking your doctor about changing to one of these. 

What special considerations are there?

While you are taking warfarin, you will need to have regular blood tests to measure your INR, to make sure that the clotting activity of the blood is within safe but effective levels. ‘INR’ stands for International Normalised Ratio and is a way of measuring the time it takes for your blood to clot. The person who prescribes your warfarin will decide what dose to give you based on the result of your INR test. In the beginning, you may need to have your INR checked almost every day, but later on it will be done usually every four to eight weeks.

If you’re taking anticoagulants, you should always carry an Anticoagulant card and remember to tell anyone treating you that you are taking anticoagulants. (An Anticoagulant card is a small card that you can show to anyone treating you, to tell them that you are taking anticoagulants.) There is usually a card in your anticoagulation treatment booklet.

Do I need to change my diet if I take Warfarin?

The amount of warfarin there is in your bloodstream can change very quickly and what you eat can also have an effect on this. Avoid cranberry juice and cranberries as they can increase the effect of warfarin, and so increase the risk of bleeding. If you’re taking warfarin and have cranberry juice or cranberries by mistake, contact your GP or anticoagulation clinic to have your blood checked, and to find out if your dose needs to be adjusted.

Foods that are high in vitamin K – such as liver, Brussels sprouts and broccoli – can prevent warfarin from working as it should. But it’s important that you eat a variety of fruit and vegetables. If you’re taking warfarin, don’t stop eating foods that are high in vitamin K. Just try and make sure you eat them regularly, rather than having them only every now and then. Having them regularly shouldn’t make a difference to your warfarin levels, as the amount of vitamin K in your bloodstream will stay fairly constant.

Alcohol can affect the level of warfarin in your bloodstream, so it is important to keep the amount of alcohol you have very low and avoid binge drinking. Long-term use of alcohol can reduce how well the warfarin works.

Can I exercise if I take Warfarin?

In general, most people who take Warfarin can exercise, as long as your doctor has given you the all clear. As a general rule of thumb, you may be advised against doing any activities that have a higher risk of accidents and therefore bleeding e.g. motor racing, contact sports, boxing, muay thai, skiing etc. The most important factor to consider when exercising is to alert another person that you will be doing some exercise, carry a medical alert card with you that contains your medical status and avoid activities that could lead to accidental bleeding. There are many other factors about exercise to consider, depending on what type of heart condition you have. Have a read here about some exercise tips. Check out my personalised programmes or get in touch to find out more about what type of exercise is appropriate for you.

Are there any interactions with Warfarin and other medications?

Oral anticoagulants interact with a number of other medicines including antibiotics, aspirin, ibuprofen and cimetidine, and also with some medicines used to treat arthritis, gout, epilepsy, high cholesterol and abnormal heart rhythms.

What side effects do I need to look for if I take Warfarin?

The main side effect of taking anticoagulants is bleeding. This happens because the anticoagulants affect the blood-clotting process, to help prevent blood clots from forming. The anticoagulants may cause internal bleeding, or make bleeding from a minor injury worse. This is more likely to happen if your INR level is too high. Make sure to keep an eye on your INR levels regularly - you should have a dedicated clinic or centre that monitors your levels and adjusts your Warfarin dosage accordingly. If you are unwell or have new medications prescribed, always inform your Warfarin centre as they may need to adjust your dose or increase the frequency of your blood tests.

Other side effects from Warfarin vary from person to person but can include hair thinning, fatigue, insomnia, bruising, gastrointestinal upset and headaches.

If you experience any of the following symptoms it could mean that your dose of Warfarin may be too high. Report these immediately.

• Cuts which bleed for longer than normal.

• Bleeding that does not stop by itself.

• Nose bleeds that last for more than a few minutes. (If a nose bleed lasts for more than 20 minutes, you must go to your GP’s surgery or to the accident and emergency department of a hospital.)

• Bleeding gums.

• Severe bruising.

• Red or dark-brown urine.

• Red or black bowel movements.

• For women, heavier bleeding during periods

This information should be read is in conjunction to the advice that your doctors, pharmacists or nurses may give you about your medication based on their knowledge of your condition but it should help you to understand what they tell you. Please ask your doctor if you have any questions at all about your medications.